Crossing the threshold

Of all objections to the government's counter-terrorism bill, the most telling comes from the director of public prosecutions, Sir Ken Macdonald. He is the man who, under the proposals, would have to authorise the detention of suspects beyond 28 days. He, more than anyone, is in a position to know whether the current limit hampers prosecutors, letting dangerous suspects go free. If he argued for a change in the law, he would be listened to. But he does not think the new power is needed.

Yesterday, appearing before the committee of MPs considering the legislation, he laid out his objections. His case is not that police can always complete their investigations within the present 28-day limit. It is that they do not need to do so because the threshold of evidence needed to bring charges in serious cases has been lowered. This, in certain circumstances, means that people can be charged on the basis of "reasonable suspicion" that they may be guilty of a crime, rather than the full test of "a realistic prospect of conviction". This point is crucial. The police, in the form of the Metropolitan commissioner Sir Ian Blair, and the home secretary say extended detention is needed because complex investigations - those involving encrypted computer files, for instance - cannot be completed in the time currently allowed. But they do not have to be. As the former lord chancellor Lord Falconer argues, "the debate about should it be 28 days, 42 days or 90 days has moved on because of the threshold standard".

This - together with the extended use of intercept evidence and post-charge questioning, which Sir Ken also called for yesterday - offers the government an honourable escape from the dead end of extended detention in which it is now trapped. Ministers are trying to force reluctant Labour MPs to support 42-day detention. They face defeat, as a whip's note leaked over the weekend suggests. This listed backbench worries: "will support but thinks barmy"; "don't think meeting Jacqui Smith three times will make any difference"; and many more. Yesterday the BBC reported that the government wants to delay the vote until mid-June, a sign that it thinks it will lose.

Why press ahead with the new power? It is unnecessary. The law as it stands is sufficient "even in the most extraordinarily complex of cases", Sir Ken said yesterday. It certainly works: 92% of terror cases produce convictions; detention beyond 14 days has been used only three times, and not at all since the June 2007 attack on Glasgow airport. Policing terror is already a difficult task. It will not be made easier by forcing through parliament a blunt new power that prosecutors do not want.